Fluid loss control flapper valve

ABSTRACT

A system for completing a well bore, comprises, a string having a housing having an inner diameter, the housing defining an inner channel, a valve seat having an inner diameter coupled to the housing, a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position; and a sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position. The flapper has an arcuate orientation that is generally concentric with the housing when the flapper is in the first open position, the flapper isolates a region of the inner channel of the housing below the flapper from a region of the inner channel of the housing above the flapper when the flapper is in a closed position, and the flapper may move to the second closed position when the sleeve is withdrawn from the inner channel of the valve seat.

BACKGROUND

The present application relates generally to the field of tools for completing subterranean wells. In particular, the application relates to downhole valves for fluid loss control.

Hydrocarbon fluids such as oil and gas are found in subterranean portions of geological formations or reservoirs. Wells are drilled into these formations for extracting the hydrocarbon fluids. However, wells must often be completed by one or more of a variety of processes before the well can be used to produce the hydrocarbon fluids from the formation. The completion processes may include perforating the well casing and/or reservoir (i.e. by use of shape charges), fracturing the formation, applying chemical treatments to the formation, gravel packing the well, or other processes.

In many applications, a single well bore may pass through more than one reservoir. In these cases, it may be desirable to complete more than one well bore zone. Accordingly, a first production zone may be completed at a down hole location. Then a second production zone may be completed in a position above (i.e. closer to the surface) the first production zone. When carrying out the completion processes above the first production zone, completion fluids (i.e. gravel slurries, propants, acidifiers, and other completion fluids) from the second production zone may migrate down hole. Additionally, the addition of completion fluids in the well bore region proximate to the second production zone may pressurize the well bore and cause completion fluids from well bore region proximate to the second production zone to migrate to the well bore region proximate to the first production zone and ultimately into the first production zone of the formation. Also, the pressurization of the well bore may cause completion fluids remaining in the well bore region proximate to the first production zone to migrate into the first production zone of the formation.

The migration of undesired completion fluids into a production zone may damage the formation and reduce the productivity of the well. Accordingly, it may be desirable to isolate the first production zone from the second production zone during the time when the first production zone has been completed and the second production zone is undergoing completion processes.

SUMMARY

One embodiment of the invention relates to a system for completing a well bore, comprising, a string having a housing having an inner diameter, the housing defining an inner channel, a valve seat having an inner diameter coupled to the housing, a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position; and a sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position. The flapper has an arcuate orientation that is generally concentric with the housing when the flapper is in the first open position, the flapper isolates a region of the inner channel of the housing below the flapper from a region of the inner channel of the housing above the flapper when the flapper is in a closed position, and the flapper, may move to the second closed position when the sleeve is withdrawn from the inner channel of the valve seat.

Another embodiment relates to a system for completing a well bore, comprising a string having a housing having an inner diameter, the housing defining an inner channel, a valve seat having an inner channel, the valve seat being coupled to the housing a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position, and the flapper being configured to be reopened by breaking the flapper into a plurality of fragments, and the inner channel of the valve seat being substantially unobstructed by the flapper when the flapper is in the open position and a sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position. The flapper has an arcuate orientation that is generally concentric with the housing when the flapper is in the first open position, the flapper isolates a region of the inner channel of the housing below the flapper from a region of the inner channel of the housing above the flapper when the flapper is in a closed position, and the flapper may move to the second closed position when the sleeve is withdrawn from the inner channel of the valve seat.

Yet another embodiment relates to a method of completing a well comprising drilling a subterranean well bore through a first production zone and a second production zone, running a completion string in the well bore, completing a region of the well bore adjacent to the first production zone, wherein completing includes delivering a completion fluid through a sleeve, at least partially isolating the region of the well bore adjacent to the first production zone by closing a flapper valve having a curved flapper, wherein closing includes partially withdrawing the sleeve from the first production zone, completing a region of the well bore adjacent to the second production zone, and opening the flapper valve.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a crossectional view of a flapper valve.

FIG. 2 is another crossectional view of the flapper valve of FIG. 1 taken along line 2-2.

FIG. 3 is a perspective view of a flapper valve.

FIG. 4 is another perspective view of the flapper valve of FIG. 3.

FIG. 5 is a crossectional view of the flapper valve of FIGS. 3 and 4 (with housing and inner sleeve).

FIG. 6 is another crossectional view of the flapper valve of FIGS. 3 and 4 (with housing and inner sleeve).

FIG. 7 is a crossectional view of the flapper valve.

FIG. 8 is another crossectional view of the flapper valve of FIG. 7.

FIG. 9 perspective view of a flapper valve.

FIG. 10 is a crossectional view of the flapper valve of FIG. 9.

FIG. 11 is another crossectional view of the flapper valve of FIG. 9.

FIG. 12 is a crossectional view of the flapper valve of FIG. 5 in wellbore.

FIG. 13 is another crossectional view of the flapper valve of FIG. 5 in wellbore.

FIG. 14 is an elevation view of a flapper for use with a flapper valve.

DETAILED DESCRIPTION

Referring to FIG. 1, a system 10 for use in a down hole well bore application. System 10 includes a housing 12 of valve 14 and a sleeve 16. Housing 12 at least partially encloses channel 13, and includes a widened portion 18. Valve 14 is placed within the widened portion 18. Valve 14 includes a flapper 20 and a flapper seat 22. Flapper 20 may be generally curved so that when the valve is in the open position the cross section of flapper 20 is curved and generally concentric with housing 12. Flapper seat 22 may be generally cylindrical and include, at an end proximate to flapper 20, a lip 24 (as shown in FIG. 3). In some applications, a seal 26 which may be elastomeric plastic or some other sealing material may be disposed on lip 24. Seal 26 serves to provide a seal between flapper 20 and flapper seat 22 when the valve is in the closed position. Alternatively, flapper 20 and flapper seat 22 may be machined to sufficient tolerances such that the valve is sealed by direct contact between flapper 20 and flapper seat 22 when the valve is in the closed position.

Sleeve 16 is positioned within valve 14 and prevents closing of flapper 20 against flapper seat 22. Sleeve 16 may be specifically included as a component of system 10. Alternatively, sleeve 16 may be a wash pipe for use in completing the well such that the presence of the wash pipe prevents valve 14 from closing while the wash pipe is in a position down hole. Once down hole completions such as, for example, gravel packing or other operations are complete, the wash pipe or sleeve 16 may be removed completely or only to a point above valve 14 such that valve 14 may be closed and held closed by a differential pressure across valve 14. Valve 14 may be used in conjunction with a cross-over tool that may be used to circulate completion fluids. Completion fluids may be delivered to the production zone through the wash pipe (sleeve 16) and be circulated by a crossover tool located below valve 14.

FIG. 2 shows system 10 including housing 12, valve 14 and sleeve 16. Valve 14 includes flapper 20 and flapper seat 22. Flapper 20 is curved to substantially match the contour of an inner wall of housing 12. The curve of flapper 20 is generally concentric with housing 12 and sleeve 16. When flapper 20 is in an open position relative to seat 22, sleeve 16 may be extended through valve 14 to retain flapper 20 in the open position. In some embodiments, sleeve 16 may be a wash pipe such as for providing completion fluids to an area of the formation down hole of valve 14. For example, a gravel slurry propent or fractioning fluid may be supplied to a down hole production zone for completion while sleeve 16 retains flapper 20 in the open position. Upon completion of the down hole production zone, sleeve 16 may be withdrawn such that flapper 20 is free to pivot into the closed position. A pressure differential across valve 14 may retain flapper 20 in the closed position. For example, the pressure in the zone above flapper 20 may be generally greater than that below flapper 20. While flapper 20 is closed, other operations may be conducted above valve 14. For example, additional production zones may be completed in the areas above flapper 20. Upon completion of all production zones and/or other work necessary to completing the well, flapper 20 may be opened. This may be accomplished by a variety of means. For example, flapper 20 may be broken into multiple pieces such that the pieces can fall down hole to a point below the production zones. This may be accomplished by over-pressurizing the zone above flapper 20 to a pressure at which flapper 20 will fail and fracture into pieces. Alternatively, a tool may be lowered, e.g., on a wire line or other device, to break flapper 20 into multiple pieces or fragments. In yet other embodiments, flapper 20 may comprise a material that may be dissolved or otherwise weakened by a fluid which may be pumped down to the area of valve 14. In these embodiments, flapper 20 may be weakened to the point that it is able to be easily fractured and the pieces fall down hole. In other embodiments, flapper 20 may be broken by applying pressure on flapper 20 by pressing sleeve 16 downwardly against closed flapper 20.

Referring to FIGS. 3 and 4, valve 14 includes a curved flapper 20, a flapper seat 22 and an attachment device 30. Flapper 20 may be coupled to flapper seat 22 by attachment device 30 which may comprise a hinge or other similar device. Attachment device 30 may be biased by a spring or other device into either the opened or closed position depending upon the application. Flapper seat 22 includes a lip 24 and a matching profile 28 in flapper 20. When in the closed position, lip 24 and profile 28 cooperate to form a seal between flapper 20 and flapper seat 22. Alternatively, a polymeric seal or other sealing device may be used to provide a seal between flapper 20 and flapper seat 22 when flapper 20 is in a closed position.

Referring to FIGS. 5 and 6, another embodiment includes a system 110 having a housing 112, a channel 113, and a valve 114. Sleeve 116 retains valve 114 in an open position. Valve 114 comprises a curved flapper 120, a flapper seat 122 and a connecting device 130. Housing 112 includes a region 132 where the wall of housing 112 has been thinned relative to other regions of housing 112. Valve 114 is in placed within region 132 and region 132 is configured such that flapper valve 120 may be retained substantially within region 132 when in the open position without substantially reducing the inner diameter of housing 112. Flapper seat 122 and flapper 120 may be configured to have thicknesses similar to the difference in thickness of housing 112 and the region 132 and other regions of housing 112. FIG. 6 shows flapper 120 in a closed position and seated flapper seat 122. Sleeve 116 has been withdrawn from housing 112.

Referring to FIGS. 7 and 8, another embodiment includes a system 210 having a housing 212 and a valve 214. Sleeve 216 retains valve 214 in an open position. Valve 214 comprises a curved flapper 220, a flapper seat 222 and a connecting device 230. Housing 212 includes a region 232 where the wall of housing 212 has been thinned relative to other regions of housing 212. Valve 214 is placed within region 232 and region 232 is configured such that flapper valve 220 may be retained substantially within region 232 when in the open position without substantially reducing the inner diameter of housing 212. Region 232 may have an arcuate profile in a region proximate to flapper 220. The arcuate profile may approximate an arc traced by flapper 220 as flapper 220 moves from a first open position to a second closed position. Flapper seat 222 and flapper 220 may be configured to have thicknesses similar to the difference in thickness of housing 212 and the region 232 and other regions of housing 212.

FIG. 8 shows flapper 220 in a closed position and seated flapper seat 222. Sleeve 216 has been withdrawn from housing 212. Upon withdrawal of sleeve 216, flapper 220 may close and form a seal with seat 222. In some embodiments, a polymer sealing member may be used to provide a seal between flapper 220 and seat 222. Flapper 220 may be biased into the closed position by springs or other means to help ensure that valve 214 closes when sleeve 216 is withdrawn. In other embodiments, flapper 220 may be oriented such that it is urged towards the closed position by its own weight. For example, in a deviated well (i.e. a non-vertical well) flapper 220, may be oriented such that flapper 220 will swing to the closed position by gravity without the use of springs or other biasing mechanisms.

Referring to FIG. 9, valve 314 includes a curved flapper 320, a flapper seat 322 and an attachment device 330. Flapper 320 may be coupled to flapper seat 322 by attachment device 330 which may comprise a hinge or other similar device. Attachment device 330 may be biased by a spring or other device into either the opened or closed position depending upon the application. Flapper seat 322 includes a lip 324 and a matching profile 328 in flapper 320. When in the closed position, lip 324 and profile 328 cooperate to form a seal between flapper 320 and flapper seat 322. Alternatively, a polymeric seal or other sealing device may be used to provide a seal between flapper 320 and flapper seat 322 when flapper 320 is in a closed position.

Valve 314 also includes an extension 334 extending from the lip 324 to a collar 336. Collar 336 may help strengthen the thinned portion of a housing in which valve 214 may be positioned. Additional extensions may be provided to couple collar 336 to valve seat 322.

Referring to FIGS. 10 and 11, another embodiment includes a system 310 having a housing 312 and a valve 314. Sleeve 316 retains valve 314 in an open position. Valve 314 comprises a curved flapper 320, a flapper seat 322 and a connecting device 330. Housing 312 includes a region 332 where the wall of housing 312 has been thinned relative to other regions of housing 312. Valve 314 is in placed within region 332 and region 332 is configured such that flapper valve 320 may be retained substantially within region 332 when in the open position without substantially reducing the inner diameter of housing 312. Region 332 may have an arcuate profile in a region proximate to flapper 320. The arcuate profile may approximate an arc traced by flapper 320 as flapper 320 moves from a first open position to a second closed position. Flapper seat 322 and flapper 320 may be configured to have thicknesses similar to the difference in thickness of housing 312 and the region 332 and other regions of housing 312. Region 332 may be generally cylindrical in shape to accommodate valve 314.

Extension 334 extends from flapper seat 322 to collar 336. Extension 332 may be provided with an opening 336 to accommodate flapper 320 when flapper 320 is in a closed position. Alternatively, extension 334 may be provided with a thinned region for accommodating a portion of flapper 320.

FIG. 11 shows flapper 320 in a closed position and seated flapper seat 322. Sleeve 316 has been withdrawn from housing 312. Upon withdrawal of sleeve 316, flapper 320 may close and form a seal with seat 322 to block channel 313. In some embodiments, a polymer sealing member may be used to provide a seal between flapper 320 and seat 322. Flapper 320 may be biased into the closed position by springs or other means to help ensure that valve 314 closes when sleeve 316 is withdrawn. In other embodiments, flapper 320 may be oriented such that it is urged towards the closed position by its own weight. For example, in a deviated well (i.e. a non-vertical well) flapper 320, may be oriented such that flapper 320 will swing to the closed position by gravity without the use of springs or other biasing mechanisms.

Referring to FIGS. 12 and 13 a well completion including the valve similar to that of FIGS. 5 and 6 is shown. However, any of the valves described herein may be substituted and the use of the valve of FIGS. 5 and 6 is for illustrative purposes only. FIG. 12 shows an embodiment including a system 410 disposed in a well bore. System 410 includes a housing 412, a channel 413, and a valve 414. Sleeve 416 retains valve 414 in an open position. Valve 414 comprises a curved flapper 420, a flapper seat 422 and a connecting device 430. Housing 412 includes a region 432 where the wall of housing 412 has been thinned relative to other regions of housing 412. Valve 414 is placed within region 432 and region 432 is configured such that flapper valve 420 may be retained substantially within region 432 when in the open position without substantially reducing the inner diameter of housing 412. Flapper seat 422 and flapper 420 may be configured to have thicknesses similar to the difference in thickness of housing 412 and the region 432 and other regions of housing 412.

Sleeve 416 is shown as a wash pipe, or part of a completion string. Housing 412 comprises a portion of a production string. A portion of housing 412 proximate to a production formation or reservoir (i.e. the portion of the formation below line A-A) includes perforations 444, and the perforated portion of housing 412 is covered by a sand screen 442. The production zone may be isolated by packer 440. Sand screen 442 may be a wire wrapped screen or other suitable filter media. Casing 438 may be perforated and the annular region between casing 438 and sand screen 442 may be gravel packed.

During completion operations, sleeve 416 may be used to provide completion fluids to the completion zone. Once the completion operations are complete, sleeve 416 may be withdrawn up the well bore to a point above valve 414. When sleeve 416 no longer prevents valve 414 from closing, flapper 420 may pivot about connecting device 430 and seal against flapper seat 422. connecting device 430 may be a hinge, and may also be biased (i.e. by a wire spring or other device) to the closed position.

FIG. 13 shows flapper 420 in a closed position and seated flapper seat 422. Sleeve 416 has been withdrawn from housing 412. Flapper 420 forms a seal by contacting flapper seat 422. Alternatively, a sealing member (e.g. a polymeric sealing member) may be provided on either flapper seat 422 or flapper 420. When valve 414 is closed, additional completions zones (not shown) may be completed above the first completion zone. Addition flapper valves may be located below a second completion zone to isolate the region between the first and second completions zones. The isolation of the region between the first and second completion zones may reduce the volume of completion fluids required to complete the second completion zone.

Once the well has been completed, the valve or valves present may be opened by a variety of means. For example, the valve may be opened by over-pressurizing the zone above flapper 420 to a pressure at which flapper 420 will fail and fracture into pieces. Alternatively, a tool may be lowered, e.g., on a wire line or other device, to break flapper 420 into multiple pieces. In yet other embodiments, flapper 420 may comprise a material that may be dissolved or otherwise weakened by a fluid which may be pumped down to the area of valve 414. In these embodiments, flapper 240 may be weakened to the point that it is able to be easily fractured and the pieces fall down hole.

Referring to FIG. 14, a flapper 520 may generally have a circular shape that is curved into a cylindrical surface. Profile 528 may be provided about a periphery of flapper 520. Lip 528 may be configured to mate with a corresponding lip or profile on a flapper seat. An annular profile 548 may be provided that is concentric with the periphery of flapper 520. Radial profiles 546 may be provided that radiate from annular profile 548 to lip 528.

Annular profile 548 and radial profiles 546, may be etched, molded, cut, or otherwise formed in the surface of flapper 520. The exact pattern of the profiles and their depths may be determined to have flapper 520 break into a desired number of pieces have a desired size. Annular profile 548 and radial profiles 546 provide weakened regions of flapper 520 such that flapper 520 will break into pieces of a desired size. While a series of annular and radial profiles are shown, other patterns may be used as well.

According to an alternative embodiment, flapper 520 may be made of a first, relatively strong material and a second weaker material. The weaker material may be used in the regions where it is desired to have flapper 520 break when flapper 520 is opened. In yet another embodiment, the flapper may comprise a first stable material and a second material that is more susceptible to corrosion, melting, salvation, or other processes such that the flapper may be broken with the application of a corrosive agent, heat, or solvent. The second material may be used in regions where it is desired to have flapper 520 break when flapper 520 is opened.

Although the foregoing has been described with reference to exemplary embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope thereof. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. The present subject matter described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements. Many other changes and modifications may be made to the present invention without departing from the spirit thereof. The scope of these and other changes will become apparent from the appended claims. The steps of the methods described herein may be varied, and carried out in different sequences. 

1. A system for completing a well bore, comprising: a string having a housing having an inner diameter, the housing defining an inner channel; a valve seat having an inner channel, the valve seat being coupled to the housing; a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position; and a sleeve positioned in the inner channel of the valve seat and configured to retain the flapper in the first open position; wherein the flapper has an arcuate orientation that is generally concentric with the housing when the flapper is in the first open position, the flapper isolates a region of the inner channel of the housing below the flapper from a region of the inner channel of the housing above the flapper when the flapper is in a closed position, and the flapper may move to the second closed position when the sleeve is withdrawn from the inner channel of the valve seat.
 2. The system of claim 1, wherein the string is a production string.
 3. The system of claim 1, wherein the string is a completion string.
 4. The system of claim 1, wherein the flapper is configured to be opened by breaking the flapper into a plurality of fragments.
 5. The system of claim 4, wherein the flapper comprises a series of profiles in a surface of the flapper, and the flapper is configured to break into the plurality of pieces generally defined by the profiles.
 6. The system of claim 4, wherein the flapper comprises a first material and a second material, and the second material is more susceptible to the effects of corrosive agents, heat, solvents, and/or pressure.
 7. The system of claim 4, wherein the sleeve is configured to apply a force sufficient to break the flapper, on the flapper after the flapper has moved to the second closed position.
 8. The system of claim 1, wherein the housing comprises a thinned portion for receiving the valve seat and the flapper.
 9. The system of claim 8, wherein the valve seat is coupled to a collar that is received within the thinned portion of the housing.
 10. The system of claim 1, wherein the inner channel of the valve seat is substantially unobstructed by the flapper when the flapper is in the open position.
 11. A system for completing a well bore, comprising: a string having a housing having an inner diameter, the housing defining an inner channel; a valve seat having an inner channel, the valve scat being coupled to the housing; a flapper pivotally coupled to the valve seat, the flapper configured to move from a first open position to a second closed position, and the flapper being configured to be reopened by breaking the flapper into a plurality of fragments, and the inner channel of the valve seat being substantially unobstructed by the flapper when the flapper is in the open position; and a sleeve positioned in the inner channel of the valve scat and configured to retain the flapper in the first open position; wherein the flapper has an arcuate orientation that is generally concentric with the housing when the flapper is in the first open position, the flapper isolates a region of the inner channel of the housing below the flapper from a region of the inner channel of the housing above the flapper when the flapper is in a closed position, and the flapper may move to the second closed position when the sleeve is withdrawn from the inner channel of the valve seat.
 12. The system of claim 11, wherein a diameter of the inner channel of the valve seat is substantially the same as the inner diameter of the housing at a position immediately downhole of the valve seat.
 13. The system of claim 11, wherein the sleeve is configured to apply a force sufficient to break the flapper, on the flapper after the flapper has moved to the second closed position.
 14. The system of claim 11, wherein the flapper comprises a first material and a second material, and the second material is more susceptible to the effects of corrosive agents, heat, solvents, and/or pressure.
 15. The system of claim 11, wherein the housing includes a valve region having a second inner diameter larger than an inner diameter of a region adjacent to the valve region, and the valve seat is disposed within the valve region.
 16. A method of completing a well comprising: drilling a subterranean well bore through a first production zone and a second production zone; running a completion string in the well bore; completing a region of the well bore adjacent to the first production zone, wherein completing includes delivering a completion fluid through a sleeve; at least partially isolating the region of the well bore adjacent to the first production zone by closing a flapper valve having a curved flapper, wherein closing includes partially withdrawing the sleeve from the first production zone; completing a region of the well bore adjacent to the second production zone; and opening the flapper valve.
 17. The method of claim 16, wherein the well is an oil or natural gas well.
 18. The method of claim 17, wherein the flapper is pivotally coupled to a valve seat having an inner channel, the flapper being configured to move from a first open position to a second closed position, and the inner channel of the valve seat being substantially unobstructed by the flapper when the flapper is in the open position.
 19. The method of claim 17, wherein the step of opening the flapper valve includes breaking the flapper into a plurality of fragments by applying pressure, corrosive agents, solvents, and/or heat to the flapper.
 20. The method of claim 17, wherein the flapper valve is coupled to the completion string. 